Real time clock generators have various applications. They can be used for providing timing information for operating systems, for enforcing policies for time-sensitive data, for assisting in positioning calculations and the like. U.S patent application serial number 2002/0083284 of Matsubara et al., titled “Data reproduction system, data recorder and data reader preventing fraudulent usage by monitoring reproducible time limit”, U.S. Pat. No. 5,920,727 of Kikinis et al., titled “Timer-controlled computer system shutdown and startup”, U.S patent application serial number 2004/0128528 of Poisner titled “Trusted real time clock” and U.S patent application serial number 2004/0225439 of Gronemeyer, titled “Method and apparatus for real time clock (RTC) brownout detection, all being incorporated herein by reference, illustrate some usages of real time clocks.
Real time clock signals can be tampered for various reasons including copyrighting piracy, concealing hacking or tampering attempts, reducing the functionality of a device and the like.
One tampering method involves repetitive alterations of the power supply level provided to the real time clock generator, in order to force the real time clock generator to reset or to get stuck.
There is a need to provide efficient methods and devices for performing voltage supply monitoring.